Cardiac catheterization. Coloured X-ray of the chest of a patient, showing a cardiac catheriza- tion procedure superimposed. The heart is seen as a shadow in the centre of the ribcage. Two catheters (white line, broken line) trace a path up to the heart from a femoral artery and vein in the leg. The white line catheter traces the arterial route around the aortic arch (at top) and into the left ventricle of the heart. The broken line catheter traces the venous route into the right side of the heart and out to a pulmonary artery of a lung. Catheterization may be used to measure blood pressure, implant sensors, or expand blood vessels by means of balloon angioplasty.